This invention concerns a method and apparatus for providing a seal between an aircraft structure and a removable panel, and an aircraft or aircraft section having such a seal.
In particular, this invention concerns a method of providing a watertight seal between an aircraft structure having an opening therein and a removable panel mountable on the structure to close the opening. The method has particular application in the sealing of interchangeable panels over aircraft chambers containing, for example, fuses and/or other sensitive equipment requiring access for maintenance and service purposes. A particular application is in the sealing of radar bay access panels on aircraft.
Conventionally, it is known to seal radar bay access panels to the surrounding aircraft structure using a polysulphide rubber compound as a sealant between the panel and a portion of the aircraft structure defining an access opening to the radar bay, the panel being attached to the structure by means of fasteners extending through the sealant compound, and grommets.
However, test procedures have established that inadequate sealing is obtained by these means and that water ingress occurs in the spaces between the fasteners. It is thought that this is due to the fasteners compressing the panel against the sealant in their immediate location but having an irregular pitch so that the panel is not properly held against the sealant compound between the fasteners when there is a relatively large spacing between them. Consequently, whilst sufficient sealing may be provided for panels covering for example standard storage spaces or relatively insensitive equipment, such sealing does not meet the requirements for electrical and other sensitive equipment.
Commercial sealant tape is also available but has not hitherto been employed for sealing panels to aircraft structures because the tape does not possess the load bearing characteristics required for such conditions.
According to the present invention, there is provided a method of providing a seal between an aircraft structure and a removable panel mountable on the structure to close an opening therein, comprising:
applying a sealant compound to either the structure or the panel,
forming a rebate in the sealant compound,
providing a sealant tape to fit within the rebate, and
fastening the panel to the structure with the seal comprising the sealant compound and the sealant tape being sandwiched between the structure and the panel and encircling the opening.
The combination of the sealant compound and the sealant tape, has been found to provide a seal which is far superior to the seal obtained by the use of either alone.
Preferably, the sealant compound is applied to the aircraft structure.
In the preferred form of the method described below, the sealant compound is then set or cured and the rebate is formed in the sealant compound at the same time, then subsequently the tape is applied to the rebate.
The sealant compound may be a polysulphide rubber compound.
According to another aspect of the invention, there is provided an aircraft or aircraft section having a structure containing an opening therein, a removable panel for closing the opening, and a seal provided between the panel and the structure, the seal comprising:
a sealant compound surrounding the opening and having a rebate formed therein, and
a sealant tape provided in the rebate.
The invention also provides apparatus for providing a seal between an aircraft structure and a removable panel mountable on the structure to close an opening therein, comprising:
means for applying a sealant compound to one of the structure and the panel,
means for forming a rebate in the sealant compound,
means for providing a sealant tape to fit within the rebate, and
means for fastening the panel to the structure with the seal comprising the sealant compound and the sealant tape being sandwiched between the structure and the panel and encircling the opening.
In addition, the invention provides a tool for use in the method, comprising a setting frame for impressing a liquid sealant compound as employed in the method and means for curing the liquid sealant compound, the frame having a substantially continuous forming surface, and a substantially continuous rib upstanding from the forming surface along the full extent thereof.